Irrigation in low volumes is noted and well known in the domain of modern agricultural irrigation. In general, the subject is an irrigation method designated to deliver the water to a specified and as accurate as practical to a defined area, with correct time and simultaneously providing nutrients (fertilizing) materials to the plants together with the water, at the correct dosage and concentration. The common range of pressures and throughput rates of the water in low volume irrigation is 0.5 to 4 atmospheres and 1 to 200 liters per hour.
There are two major low volume irrigation methods—drip irrigation and irrigation by sprinkling.
The drip irrigation method is based on a system of drip emitters. It is possible to describe a drip emitter as a device accepting water under pressure. The drip emitter reduces the water pressure by directing the water flow through a mechanical mechanism where it encounters resistance to the flow. For example, passing the water through a flow passage formed with a labyrinth of pointed/sharp barriers (set of baffles) positioned in the flow path of the water. The barrier's labyrinth abates and reduces the water pressure. Thus, following it “journey” through the drip emitter, the water at reduced pressure exits the drip emitter as a dripping current.
The advantages of using low volume irrigation through drip emitters, lies in the fact that it brings the water to very accurate designated locations. It also enables providing exact dosages of water and fertilizers, and the drip emitter system can be hidden preventing physical damage to the system combined with inhabiting herbage growth.
The disadvantages of using low volume irrigation through drip emitters, is its “pointed” mode of irrigation. Considering its cross section, the wetted volume resembles an “onion” shaped volume that only its relatively small upper (top) layer is located at the upper ground level. But it is this specific layer that is reckoned as critical for developing the roots system of the plants—which is the layer that should be irrigated (as it is richer in fertilizers contents and oxygen percentages). In order to overcome this drawback, farmers tend to increase the number of drip emitters per area unit. This solution—increasing the density of branches and of drip emitters per branch, obviously reduces the advantage of employing the drip emitters method, because the quantity of required equipment increases significantly (and also the deployment tasks become more costly and difficult).
A known and noted product in the domain of low volume irrigation by drip emitters is an “Integral Drip Line”, the so-called “In-Line Drip Line”. This is a tubular conduit, that simultaneously with its production process (for example, by a continuous extruding process as a tubular profile or made up from two sheets that are connected flush one to the other at the edges, resulting in a tube with two seams or formed as a tube from a folded sheet that is eventually made as a tube with one seam—along its length), drip emitters units being included within it and embedded in it, located along its length with selected gaps between each and its adjacent members.
In an “Integral Drip Line” or in other words—“In-Line Drip Line”, the drip emitter units might be cylindrical (and in this case they are implanted within the tube in all their circumferential area—see for example Eckstein's U.S. Pat. No. 3,981,452), or flat (and then they are fixed to the inner surface of the tube only in part of their circumferential area), (see for example Gorney et al's U.S. Pat. No. 4,728,042).
Exact opening of apertures (“openings”) in the tube, exactly at the appropriate locations, namely exactly facing the water exits that are formed in the drip emitter units located in the tube along its length, complete the process of producing the integral drip line. Thus, the water flowing within the tube, are shed from it at the appropriate locations, dripping as required.
Processes and means for manufacturing integral drip lines simultaneously with the manufacturing process of the tube are familiar and known since long ago. (see for example Mehoudar's U.S. Pat. No. 5,022,940 covering manufacture of integral drip line in a continuous extruding process of a tubular profile and DeFrank's et al U.S. Pat. No. 5,522,551 relating to manufacturing integral drip lines from a sheet folded to eventually form a tube with a seam).
An outstanding advantage of the integral drip line is the ease of operating it in the field. Deploying the integral drip line and collecting it back (as a large coil) is done with relative ease. The structure of the system also protects the emitter units against physical damage (as they are embedded within the tube and not protruding from it). Because of this advantage, more and more farmers are switching over to irrigation with integral drip lines. Aided by suitable mechanization means, deploying the tubes is done efficiently and all the farmer has to do is to connect it to a water source and close its other end.
As we have pointed above, installation of the integral drip line for operation in the field might be mechanized, and hence efficient and at low cost, but the integral drip line do not offer an answer to the problem we posed above—namely the drawback of missing the localized irrigation, namely the deterrent small area on the ground that is wetted by the drip emitters.
Referring to FIG. 1a, FIG. 1a is an illustration of existing prior art as cited above, relating to low volume irrigation by employing a sector of integral drip line 10 that is laid on the ground (marked by line 15). Drip emitters 20 and 25 embedded within tube 10 at the time of its production (illustrated by dashed lines) form wetting patterns inside the ground, in the image of “onions” 30 and 35. The relatively small wetted areas on the ground surface wetted by the drip emitters are seen rather distinctively. On the other hand, the relative ease and simplicity of deploying the system, i.e., extending tube 10 on the ground is self-evident.
As cited, there is an additional common method in use for low volume irrigation—irrigation by sprinkling. Irrigation by sprinkling is based on using systems of mini sprinklers. A mini sprinkler is a device relatively complicates (a sprinklers' post might be assembled from five to ten parts). Mini sprinklers are described, for example, in Hemsley et al's U.S. Pat. No. 4,889,287.
The farmer is required to deploy a water supply hose in the intended location. Then, he installs the posts for the sprinklers along the hose and in close proximity. Generally, the farmer receives the sprinklers' posts already in their assembled state, and is required to stabilize them on the ground near the water hose he deployed on the ground, for example—by tying them to a pegs driven into the ground or by tying the sprinklers unto a wire that was laid beforehand. Additional tasks that the farmer has to perform are prying holes in the water hose and connect the sprinklers posts to provide a water passage from the hose to the sprinklers.
The advantages of the low volume irrigation by mini sprinklers, is that it wets—simultaneously, a relatively large area on the upper ground surface, and hence exploits in an optimal mode the ground upper layer that is best suited for developing the roots. If the farmer manages to deploy the sprinkler's post at beneficial gaps one from each other, correctly allowing for weighting the water supply rates versus water losses (due to winds, and evaporation to the air) then on the ground—the wetted area that would be obtained, would nor be a collection of separate localized points (as would have been obtained for low volume irrigation using drip emitters), but rather a relatively large assemblage of wetted surfaces that together combine to one large area sector. Instead of the former mentioned “onion” like cross section (as would have been obtained for low volume irrigation using drip emitters), a wide wetted area would be provide, that would prompt a better roots development in the critical ground layer, combined with a more efficient rinsing and driving away salts that accumulate in the ground surface (especially in dray air areas). Thus a micro weather change to the better would be generated—through reducing the temperature and increasing the humidity below the vegetation growth scene, and generating a growth environment that hides the fertilizers spread on the ground.
On the other hand, the drawbacks of the low volume irrigation by the mini sprinklers method, lies in the relative complicity required for performing the multi stages installation of the system correctly and efficiently (as we enumerated: deploying the water hose, installing and anchoring the sprinkler's posts at its vicinity and with suitable gaps between them, connecting water piping from the hose to the sprinklers). Naturally, from the complications linked to the installation, we can understand the costs issue facing the farmer. Deploying the sprinklers system in the field is not mechanized and thus neither efficient nor cheap. The sprinklers assemblage is exposed to the environment and also to physical harm, and disassembling it requires all the above mentioned complicated steps (done backwards: disconnecting the water supply, dismantling the sprinklers from the posts, disassembling each post separately).
Referring to FIG. 1b. FIG. 1b displays prior art, regarding the execution of low volume irrigation using the mini sprinkler units system 50. A water hose 55 is deployed at the intended destination on the ground surface (marked by line 60). The farmer installs the sprinklers 65 and 70, along and in the proximity of hose 30. In the illustrated example, sprinklers 65 and 70 are stabilized on pegs 75 and 80, respectively, that are driven into the ground. Water hose 55 is perforated and connected, through tubes 85, 90 respectively, in order to provide a water flow into the sprinklers. Sprinklers 65 and 70 generate by their concurrent action, circumferential wetted sectors 95 and 100, which cover a relatively large area on the upper ground surface. On the ground, the wetted area that would be received from the system 50, would not be a collection of localized points (as would have been obtained for low volume irrigation using drip emitters, see FIG. 1a), but rather an array of wetted areas that together form a relatively large wide and continuous volume. On the other hand, the complications linked to the deployment and dismantling of the system on all the required stages, depict the difficulties clearly and unequivocally.
A wide and continuous wetted volume is also required in additional applications, that are not necessarily agricultural, in which use is made of low volume irrigation systems. For example—a method for rinsing minerals (heap leaching) by using solutions that are distributed by sprinklers or spread through drip emitters, (for example, on the heaps of material that was dug from a mine), (see for example Herndon's U.S. Pat. No. 4,739,973). Any professional experienced in this field would understand that the workers in a mine that wish to use existing systems such as reviewed above (sprinklers or drip emitters) encounter actually the same drawbacks that were encountered by the farmers, as described above.